US1193800A - Waltek s - Google Patents

Description

W. S. LANDIS.

CATALYZER FOR OXI DIZING AMMONIA. APPLICATION FILED 1mm, 1916.

1,193,800 Patented Aug. 8, 1916.

zgwuemho z WaLCer' S. Lem/dis, 4y

Gum/way UNITED OFFICE.

WALTER s. mums, or ruw roan, 1mm, ammo rmx s. WASI-IBUBN, or

. I NASHVILLE, TENNESSEE.

cA'rnLYzEn FOR oxrnrzmo AMMONIA.

' Specification of Letters Patent.

Original application flied February 20,1915, Serial No. 9,596. Divided and this application filed January 27, 1916. Serial No. 74,673.

oxidizing ammonia and has for its object to produce nitrose gases in a manner more efficient and less costly than has been heretofore proposed.

With these andother objects in view the invention consists in the novel construction constituting my ap aratus, all as will be more fullyhereina er disclosed and particularly pointed out in the claims.

In my copending application, Serial No. I

9596 filed February 20, 1915, and entitled u Processof and apparatus for oxidizing am- I monia, of which this application is a division, I disclose and claim a method of oxidizingammonia for which the apparatus made the subject of this application is suitable. Also in my copending application Serial No. 9595, filed February 20,1915 and entitled Method of oxidizing ammonia I disclose certain reactions that are involved in the oxidation of ammonia to nitrose gases,

and how'the precooling of the gas mixture before striking the catalyzer gives rise to a much higher efliciency than is found in the older methods which do not employ-this cooling action. But in the use of a cooler there is naturally brought forward prorninently the necessity 10f providing special means for supplying the required amount of outside heat, to the reacting mixture in order that the flame may burn continuously.

I have found that when one uses an ammonia air mixture in the proportion of one volume of ammonia to 15 volumes of air the resulting flame temperature is'only about 460 C. and inasmuch as this combustion takes'place best at temperaturesof slightly above 700 C. I .find with such proportions 2670 cals. per cubic meter of ammonia Patented Aug. 8, 191 16. 7

burned. Even in case one oper'ateswith a mixture of one volume of ammonia to ten volumes of air the resulting flame temperature is only 640 C. and there is a deficiency of 470 cals. per cubic meter of ammonia" burned. On. the other hand, similar calculations show that if a mixture of one volume of ammonia to 7% volumes of air could be used the resulting flame temperature, allow ing for slight losses, would be just about right for the proper working of the catalyzer. But again, when a mixture of am monia and air containing less air than .one volume of ammonia to ten volumes of air is used it does not operate well from a chemicalvariable amount of heat, the quantity vdepending upon the ratio of ammonia to air which one desired to use. Of course, if one uses an enriched air, such as the waste gases from a liquid air plant, producing nitrogen,

or if one employs purposely enriched gases made by introducing'oxygen into air in any well known manner, this deficiencyof heat 1 will disappear with an increase of the oxygen content of the air used. It is however, necessary to meet a varying 'heat requirement in the reaction, even when operating with various kinds and proportions of enriched air. j

It is under all circumstances necessary to supply heat inorder to start the reaction going, and this can best be done by preheating the catalyzer until the flame ignites" and burns steadily. I, therefore, see that in a commercial operation of an ammonia oxi dation plant it is necessary to provide means, not only of heating the catalyzer, but of controlling .the amount of heat one supplies to this apparatus.

I am well awarethat the most advantageous system of supplying heat that must be accurately controlled, is through transformposition of a suitable resistance.

7 trolling means 5.

ing electrical energy into heat by the inter- And the ease with which this electrically generated heat can be controlled to an exactness which is so essential to this process makes it an added feature'of the process.

I am also aware that many years ago laboratory experiments were carried out in which platinum spirals were heated in a current of an ammonia-air mixture, forming nitric acid. These experiments, however, were only of scientific interest because the yields were extremely low and a very large percentage of nitric acid which might have been formed was subsequently decomposed by remaining in contact with the electrically heated spirals. The objections to the above processes have been overcome by my process now to be disclosed. That is to say, I have discovered a principle by which high efficiencies of oxidation are attained on a commercial scale, adapted to produce hundreds of pounds of nitric acid daily. In the first place, I use a new form of catalyzer, coupled with the use of electrical energy for supplying the necessary heat to maintain the necessary reacting temperature in the apparatus.

The previous forms of catalyzers used so far as Iam aware have consisted of platinum tubes, various complex combinations of sheets and tubes, interlacing of platinum sheet, platinized mica, and even platinized asbestos as well as platinum sponge. None of these, however, lend themselves readily to electrical heating because their construction does not afford a uniform resistance throughout the catalyzer, and therefore, there will be some local overheating should an electrical current be passed through them. It is very important in this processthat the catalyzer be absolutely uniformly heated, as exact temperature control is an important part of the oxidation process. I therefore,

use for my catalyzer a gauze or fabric woven from uniformly drawn platinum wire, and supported on a suitable frame, all as will be clear from the accompanying drawings forming a part of this specification in which Figure 1 is a diagrammatic plan view of a catalyzer. apparatus made in accordance With my invention; and Fig. 2 illustrates an oxidation chamber containing a cooler associated with such'a catalyzing device.

In the said drawings 1 represents any suitable frame preferably of insulating material upon which is mounted the platinum mesh or wire cloth 2; The said cloth or meslr2 is joined in the circuit 3 with a suitable generator or other source of current 4 and with the rheostat or other current con- By employing one or more catalyzers such as illustrated in the oxidation chamber 12,

provided with a cooler 13, inlet 14, and outlet 15 in the manner disclosed in my said application, Serial No. 9595 above, I can heat the catalyzer material uniformly with an electric current, and by means of a suitable rheostat can maintain the temperature at any point desired.

I have found thatthe platinum gauze with wires of say .005 of an inch in diameter or less, and with meshes of say 60 to the inch serves very well, and that the diameter of the wire and number of meshes have little influence provided they are of dimensions less than those above stated. By inserting such a catalyzer in my apparatus I can heat it electrically to the desired temperature, and pass a current of an ammonia-air mixture through it attaining practically 100% efficiency in oxidation.

By means of the electrical control, consisting of either a resistance or a variable voltage transformer I can vary the heat generated in this form of catalyzer to correspond to the varying proportions of ammonia to air in the mixture, whether using air alone, or oxygen enriched air. Or in case I have suflicient oxygen in my enriched air, I can simply use this electrical energy for starting the reaction, after which it will take care of itself.

In case the amm0nia-air mixture is not enriched by oxygen, it is found desirable to uniformly heat the catalyzer material above 500 C. and usually up to about 700 C. or higher, depending on the proportions of air and ammonia actually employed. It is also desirable to cool the mixture as much as possible before subjecting it to the action of the catalyzer, and to this end I may cool the mixture to any desired degree by passing it through suitable refrigerating coils before leading it to the oxidizing chamber, thereby facilitating the further cooling action of the apparatus 13in said chamber. The best form of catalyzer I have found for this purpose, is one made of iridium free platinum. In other words, I find if even a very small quantity of iridium is present in the plat inum, it greatly decreases the efliciency of the catalyzer.

It is evident that those skilled in the art may vary the details of my apparatus without departing from the spirit of the invention, and therefore I do not wish to be limited to the above disclosure except as may be required by the claims.

What I claim is 1. The herein described new catalyzer element comprising a wire gauze of iridium free platinum.

2. The herein described new catalyzer element comprising a wire gauze woven from a uniformly drawn wire of iridium free platinum.

.3. The herein described new catalyzer element comprising a wire gauze fabric com- In testimony whereof I afiix my signature, posed 'of uniformly drawn wire of iridium in presence of two Witnesses.

free platinum joined in an electric circuit, WALTER S. LANDIS. combined with means for controlling the Witnesses: 5 energy passing through said circuit, sub- G. M. SOHURMAN,

stantially as described. S. W. MAYS.

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